Как работают RFID

Kevin Bonsor

Длинные очереди перед кассами в гастрономе вызывают жалобы многих. Скоро, они могут исчезнуть, когда вездесущий (UPC) штриховой код Универсальный Код Продукта заменится умными этикетками, названными радиочастотными (RFID) идентификационными метками. Метки RFID по существу являются интеллектуальными штриховыми кодами, которые могут переговорить по сети с системой, и отследить каждый продукт, что Вы кладете в вашу тележку.

Photo courtesy Motorola Smart labels like Motorola's BiStatix tags will enable manufacturers to track their products at all times.

Imagine going to the grocery store, filling up your cart and walking right out the door. No longer will you have to wait as someone rings up each item in your cart one at at time. Instead, these RFID tags will communicate with an electronic reader that will detect every item in the cart and ring each up almost instantly. The reader will be connected to a large network that will send information on your products to the retailer and product manufacturers. Your bank will then be notified and the amount of the bill will be deducted from your account. No lines, no waiting.

RFID tags, a technology once limited to tracking cattle, will soon be tracking trillions of consumer products worldwide. Manufacturers will know the location of each product they make from the time it's made until it's used and tossed in the recycle bin or trash can. In this article, you'll learn about the types of RFID tags in development and how these smart labels will be tracked through the entire supply chain.

Reinventing the Bar Code

Barcodes, like this one found on a soda can, are found on almost everything we buy.

Almost everything that you buy from retailers has a UPC bar code printed on it. These bar codes help manufacturers and retailers keep track of inventory. They also give valuable information about the quantity of products being bought and, to some extent, by whom the products are being bought. These codes serve as product fingerprints made of machine-readable parallel bars that store binary code.

Created in the early 1970s to speed up the check out process, bar codes have a few disadvantages:

• In order to keep up with inventories, companies must scan each bar code on every box of a particular product.
• Going through the checkout line involves the same process of scanning each bar code on each item.
• Bar code is a read-only technology, meaning that it cannot send out any information.

Let's look at two types of smart labels that have read and write capabilities, which means that the data stored on these labels can be changed, updated and locked.

Inductively Coupled RFID Tags

This type of RFID tag has been used for years to track everything from cows and railroad cars to airline baggage and highway tolls. There are three parts to a typical inductively coupled RFID tag:

• Silicon microprocessor - These chips vary in size depending on their purpose
• Metal coil - Made of copper or aluminum wire that is wound into a circular pattern on the transponder, this coil acts as the tag's antenna. The tag transmits signals to the reader, with read distance determined by the size of the coil antenna. These coil antennas can operate at 13.56 MHz.
• Encapsulating material - glass or polymer material that wraps around the chip and coil

Inductive RFID tags are powered by the magnetic field generated by the reader. The tag's antenna picks up the magnetic energy, and the tag communicates with the reader. The tag then modulates the magnetic field in order to retrieve and transmit data back to the reader. Data is transmitted back to the reader, which directs it to the host computer.

RFID tags are very expensive on a per-unit basis, costing anywhere from $1 for passive button tags to $200 for battery-powered, read-write tags. The high cost for these tags is due to the silicon, the coil antenna and the process that is needed to wind the coil around the surface of the tag.

Capacitively Coupled RFID Tags
Capacitively coupled RFID tags have been created in an attempt to lower the cost of radio-tag systems. These tags do away with the metal coil and use a small amount of silicon to perform that same function as a inductively coupled tag. A capacitively coupled tag also has three parts:

• Silicon microprocessor - Motorola's BiStatix RFID tags use a silicon chip that is only 3 mm². These tags can store 96 bits of information, which would allow for trillions of unique numbers that can be assigned to products.
• Conductive carbon ink - This special ink acts as the tag's antenna. It is applied to the paper substrate through conventional printing means. (For more information, read How Printable Computers Will Work.)
• Paper - The silicon chip is attached to printed carbon-ink electrodes on the back of a paper label, creating a low-cost, disposable tag that can be integrated on conventional product labels.

By using conductive ink instead of metal coils, the price of capacitively coupled tags are as low as 50 cents. These tags are also more flexible than the inductively coupled tag. Capacitively coupled tags, like the ones made by Motorola, can be bent, torn or crumpled, and can still relay data to the tag reader. In contrast to the magnetic energy that powers the inductively coupled tag, capacitively coupled tags are powered by electric fields generated by the reader.

The disadvantage to this kind of tag is that it has a very limited range. The range of Motorola's BiStatix tags is limited to just about 1 cm (.39 inch). Making the tag cover a larger area of the product packaging will increase the range, but not to the extent that would be ideal for the system that retailers would want. In order for a global system of trillions of talking tags to work, the range needs to be boosted to several feet or more. Intermec has developed RFID tags that meet these needs, but that are too expensive to be cost-effective.

Researchers at several companies are looking for ways to create a tag with a range of several feet, but that costs about the same as bar code technology. In order for retailers to implement a widespread RFID tag system, the cost of the tags will have to get down to one penny (1 cent) per tag. In the next section, you will learn how these tags will be used to create a global system of tags that link to the Internet.

Talking Tags
When scientists are able to increase the range and lower the price of RFID tags, it will lead to a ubiquitous network of smart packages that track every phase of the supply chain. Store shelves will be full of smart-labeled products that can be tracked from purchase to trash can. The shelves themselves will communicate wirelessly with the network. The tags will be just one component of this large product-tracking network to collect data.

The other two pieces to this network will be the readers that communicate directly with these smart labels and the Internet, which will serve as the communications lines for the network. Readers could soon be everywhere, including home appliances and gadgets. In fact, readers could be built directly into the walls during a building's construction becoming a seamless, unseen part of our surroundings.

Let's look at a real-world scenario of how this system might work:

• On a typical trip to the grocery store, one of the items on your shopping list is milk. The milk containers will have a smart label that stores the milk's expiration date and price. When you pick up the milk from the shelf, the shelf may display that milk container's specific expiration date or the information could be wirelessly sent to your personal digital assistant or cell phone.
• The milk and all of the other items you've picked up at the store are automatically tallied as you walk through the doors that have an embedded tag reader. The information from the purchases you've made are sent to your bank, which deducts the amount of the bill from your account. Product manufacturers know that you've bought their product and the store's computers know exactly how many of each product that need to be reordered.
• Once you get home, you put your milk in the refrigerator, which is also equipped with a tag reader. This smart refrigerator is capable of tracking all of your groceries stored in it. It can track the foods you use, how often you restock your refrigerator and can let you know when that milk and other foods spoil.
• Products are also tracked when they are thrown into a trash can or recycle bin. At this point, your refrigerator could add milk to your grocery list, or you could program it to order these items automatically.

In order for this system to work, each product will have to be given a unique product number. MIT's Auto-ID Center, created a couple of years ago, is working on an Electronic Product Code (EPC) identifier that could replace the UPC. Every smart label could contain 96 bits of information, including the product manufacturer, product name and a 40-bit serial number. Using this system, a smart label would communicate with a network, called the Object Naming Service. This database would retrieve information about a product and then direct information to the manufacturer's computers.

The information stored on the smart labels would be written in a Product Markup Language (PML), which is based on the eXtensible Markup Language (XML). PML would allow all computers to communicate with any computer system in a similar way that Web servers read Hyper Text Markup Language (HTML), the common language used to create Web pages.

Researchers believe that smart labels could be on your favorite consumer products very soon. Once the technical challenges are overcome, the only obstacle might be the public's reaction to a network system that can track every thing that they buy and keep in their kitchen cabinets.

Bar Code History

At 8:01 a.m. on June 26, 1974, a customer at Marsh's supermarket in Troy, OH, made the first purchase of a product with a bar code, a 10-pack of Wrigley's Juicy Fruit Gum. This began a new era in retail that sped up check-outs and gave companies a more efficient method for inventory control. That pack of gum took its place in American history and is currently on display at the Smithsonian Institute's National Museum of American History.

That historical purchase was the culmination of nearly 30 years of research and development. The first system for automatic product coding was patented by Bernard Silver and Norman Woodland, both graduate students at Drexler Institute of Technology. They used a pattern of ink that glowed under ultraviolet light. This system was too expensive and the ink wasn't too stable. The system we use today was unveiled by IBM in 1973, and uses readers designed by NCR.

Источник -- http://electronics.howstuffworks.com/

Lots More Information

Related HowStuffWorks Articles

• How UPC Bar Codes Work
• How Anti-shoplifting Devices Work
• How Radio Works